802.11ad Guide - Wireless at 60GHz

802.11ad - WLAN at 60 GHz
A Technology Introduction
White Paper
Data rates in the range of several Gigabit/s are needed to transmit signals like uncompressed video sig-
nals. Amendment 802.11ad to the WLAN standard defines the MAC and PHY layers for very high through-
put (VHT) in the 60 GHz range.
This white paper provides an introduction to the technology behind 802.11ad and highlights the test and
measurement requirements.
Note:
Please find the most up-to-date Application Note on our homepage http:www.rohde-schwarz.com/
appnote/1MA220.
WhitePaper
WLAN 802.11ad ─ 1MA220_2e
BernhardSchulz-1MA220_2e

Contents802.11ad - WLAN at 60 GHz
2White Paper WLAN 802.11ad ─ 1MA220_2e
Contents
1 Introduction............................................................................................ 3
2 Key Features...........................................................................................5
3 The 11ad Physical Layer (PHY).............................................................6
4 Measurement requirements................................................................ 21
5 Appendix...............................................................................................25
6 Rohde & Schwarz.................................................................................28

Introduction802.11ad - WLAN at 60 GHz
1 Introduction
Digital wireless communications will always demand more throughput than is available.
Especially when several users must share the same physical resources, only a fraction
of the nominal throughput remains. Multimedia data streams in particular require very
high throughput on a continuous basis. One example is uncoded 3D high definition
video streams (currently at 4k resolution (Ultra-HD: 3840 x 2160 pixels), and the trend
is toward higher frame rates of e.g. 48 frames per second).
To meet this need, the Wireless Gigabit Alliance (WiGig) has developed a specification
for wireless transmission of data in the 60 GHz band at speeds in the multi-Gigabit
range.
Why the 60 GHz band?
In the range around 60 GHz, an unlicensed frequency band is available everywhere in
the world. This range permits higher channel bandwidths for greater throughput.
Another advantage is the small wavelengths (approx. 5 mm). These make it possible to
use compact and competitive antennas or antenna arrays (e.g. for beamforming).
At first glance, however, this range also has some apparent disadvantages:
● very high free field attenuation in this band. (attenuation after 1 m: 68 dB, after 10
m: 91 dB)
● oxygen (O2) absorption
However, because the transmission typically takes place within a limited range of
under 10 m (the typical living room), the high degree of attenuation can also be seen
as an advantage. Interference from adjacent transmissions is very unlikely. The trans-
mission is very difficult to intercept, making it even more secure. Finally, beamforming
can be used to focus the power to the receiver.
WLAN 802.11
The 802.11 WLAN standard has also been continuously updated to permit higher
throughput. These changes were developed as amendments, but have since been
assigned their own letter as enhancements to the standard using the MAC and PHY
layers. The relevant standard enhancements are 11a,b,g,n and these cover the two
bands in the 2.4 GHz and the 5 GHz range. The 11n extension (also called High
Throughput (HT)) uses up to four MIMO streams to achieve a data rate of up to 600
Mbit/s. The 11p standard is an extension that permits robust data traffic between auto-
mobiles (car to car).
You can read more about the various standards in The WLAN Universe [3]. For T&M
possibilities using Rohde & Schwarz instruments, refer to
● http:www.rohde-schwarz.com/appnote/1MA169
● http:www.rohde-schwarz.com/appnote/1EF82

Introduction802.11ad - WLAN at 60 GHz
The latest developments are known as Very High Throughput (VHT) and are specified
in two new amendments:
● 11ac is intended for the frequency range under 6 GHz and uses "conventional"
technologies, such as those seen in 11n. It uses bandwidths of up to 160 MHz and
eight MIMO streams to achieve data rates of more than 1 Gbit/s for the 80 MHz
bandwidth (see http:www.rohde-schwarz.com/appnote/1MA192).
● 11ad covers the frequency range at 60 GHz. The WiGig standard mentioned above
was fully integrated into 11ad.
Chapter 2 provides an overview of the key features.
Chapter 3 provides a detailed explanation of the three different PHYs being used and
highlights the differences.
Chapter 4 describes the T&M requirements.

Key Features802.11ad - WLAN at 60 GHz
2 Key Features
802.11ad includes the following key features:
● Support for data rates of up to 7 Gbit/s, divided into
– a mode with simple, robust modulation, but lower data rates (single carrier),
– an energy-saving mode for battery-operated devices (single carrier low power)
– and a high-performance mode with OFDM technology for very high throughput
● Use of the 60 GHz unlicensed band
– provides global availability
– avoids the overcrowded 2.4 GHz and 5 GHz bands
– uses short wavelengths (5 mm at 60 GHz), making compact and affordable
antennas or antenna arrays possible
● Beamforming
– optimizes power at the receiver.
– overcomes interference (changes in the channel conditions) during the trans-
mission in realtime
● is backward compatible with the WLAN universe
– Seamless use of 802.11a,b,g,n
– across both bands 2.4 GHz and 5 GHz, plus 11ad in the 60 GHz range -> "tri-
band" devices
Typical applications for 11ad are:
● Wireless Display
● Distribution of HDTV content (e.g. in residential living rooms)
● Wireless PC connection to transmit huge files quickly
● Automatic sync applications (e.g. uploading images from a camera to a PC, "kiosk"
applications)

The 11ad Physical Layer (PHY)802.11ad - WLAN at 60 GHz
3 The 11ad Physical Layer (PHY)
The 11ad physical layer was added as an amendment, chapter 21 of the 802.11-2012
standard. It is called "Directional Multi-Gigabit (DMG) PHY". This chapter provides a
detailed description of the various implementations.
3.1 Channels
The nominal channel bandwidth is 2.16 GHz. The useful ISM band around 60 GHz (57
GHz to 66 GHz) is regulated differently in various regions of the world. Four channels
are defined for this band, but they are not universally available. Channel 2 is available
in all regions and is therefore used as the default channel.
Table 3-1: Channel numbers in the 60 GHz band
Channels
1 58.32 GHz
2 60.48 GHz
3 62.64 GHz
4 64.80 GHz
Figure 3-1: Channels in the 60 GHz band
A transmitter operating in this band must match a spectrum mask; see Chapter 4,
"Measurement requirements", on page 21.
Channels

3.2 Directional multi-Gigabit (DMG): Three different PHYs.
In principle, three different modulation modes are available. They make it possible to
fulfill differing requirements (such as high throughput or robustness). Not all three
modes need to be supported by every implementation:
Table 3-2: Three different PHYs.
PHY MCS Anmerkung
Control PHY 0
Single carrier PHY (SC PHY) 1...12
25...31 (low power SC PHY)
OFDM PHY 13...24
All DMG PHYs use the same packet structure, but they differ in how the individual
fields are defined as well as in the coding and modulation that is used.
Figure 3-2: General structure of a packet in 11ad.
A packet is made up of the following common parts:
● Preamble
The preamble consists of the short training field (STF) and the channel estimation
(CE) field. It is required in every packet. It supports the receiver during automatic
gain control (AGC), when recognizing the packet and in estimating the frequency
offset, and it displays the type of PHY that is used (SC or OFDM). The receiver can
also use the known CE field to estimate the channel.
● Header
The header is different for every PHY and contains additional important information
for the receiver, such as the modulation mode (MCS), the length of the data field or
a checksum.
● Data
This part is used to transmit the actual data with different modulations (MCS). The
length of the field varies (number of bytes/octets).
● TRN
This field is optional and can be appended to all packets. It includes beamforming
information (see Chapter 3.3, "Beamforming", on page 16)
Individual fields in the packets (e.g. the preamble) are made up of Golay sequences
(see Chapter 5.1, "Golay sequences", on page 25) Each sequence consists of bipo-
lar symbols (±1). They are constructed mathematically in order to achieve specific
auto-correlation characteristics. Each consists of a complementary pair (a and b). An
Directional multi-Gigabit (DMG): Three different PHYs.

additional index contains the length of the sequence. For example, Ga128 and Gb128
represent a complementary sequence with a length of 128. In addition, four specific
Gx128 are then logically combined into Gu512 or Gv512
The single carrier PHYs (SC, low power SC and control) nominally use a bandwidth of
1760 MHz, while the OFDM PHY uses 1830.47 MHz.
3.2.1 Control PHY
This mode is used to exchange signaling and/or control messages in order to establish
and monitor connections between the various devices. Support for this mode is there-
fore mandatory for all devices. MCS0 was selected to provide very robust transmission
that can withstand possible interference in the channel. BPSK modulation is used and
the preamble (STF) is longer than in the other packets to make the transmission more
robust.
Figure 3-3: Control packet preamble: STF consists of 50 G128 sequences and CE transmits Gu + Gv.
The STF is made up of a total of 50 G128 sequences. Gb128 is first repeated 48 times,
followed by one –Gb128 and one –Ga128. As a result, the STF is 50*128 = 6400 Tc in
length. The CE field consists of one Gu512 and one Gv512 , followed by a –Gb128
sequence. The same CE field is also used for SC PHY. As a result, the CE field is
9*128 = 1152 Tc in length.

Figure 3-4: Control packet header (40 bits).
The control header is a total of 40 bits in length. The most important fields are
explained here:
● Scrambler initialization: Provides the start point for the scrambler (see Figure 3-5)
● Length (data): Specifies the length of the data field. For control, the range is 14
octets to 1023 octets
● Packet type: Specifies whether the beamforming training field is intended for the
receiver or the transmitter. It carries no information when Training Length = 0
● Training length: Specifies whether a beamforming training field is used and if so,
how long it is
● HCS: Provides a checksum per CRC for the header
The data to be transmitted is scrambled, coded, modulated and spread.
Figure 3-5: Control packet: Data processing.
● The scrambler is the same for all PHYs; only the initialization value is set differently
(transmitted in the header)
● For the encoding, a low-density parity check (LDPC) coder is used. It always uses
a codeword length of 672 bits, and the coding rate varies depending on the PHY.
The 3/4 matrix with shortening is used here, which results in a code rate of 1/2 or
less.
● Differential BPSK is used as a robust modulation. It is shifted by π/2 to avoid zero
crossings in the I/Q diagram. As a result, the difference between the peak and
average power remains low.
● Finally, the signal is spread with a Ga32 sequence.

3.2.2 Single Carrier modes
In SC mode, from 385 Mbit/s up to 4.620 Gbit/s are transmitted depending on the
MCS. To support mobile devices that are sensitive to power consumption, an addi-
tional (optional) low-power SC mode with an energy-saving encoder is defined.
Figure 3-6: SC packet preamble: STF consists of 17 Ga128 sequences and CE transmits Gu + Gv.
The basic packet structure is the same for both SC types. In the case of the low-power
PHY, the 16QAM modulation is not used during data transmission in order to save
energy. The STF is made up of a total of 17 G128 sequences. Ga128 is first repeated
16 times, followed by one –Ga128. As a result, the STF is 17*128 = 2176 Tc in length.
The CE field consists of one Gu512 and one Gv512, followed by a –Gb128 sequence.
As a result, the CE field is 9*128 = 1152 Tc in length. The same CE field is also used in
the control PHY.
Figure 3-7: SC packet header (64 bits).
The SC header is a total of 64 bits in length. The most important fields are explained
here:

● MCS: Displays the modulation and coding scheme used in the data field
● Length (data): Specifies the length of the data field. For control, the range is 1 octet
to 262143 octets
how long it is
● Last RSSI: Displays the power level of the last field received
The additional steps for the data field differ for SC PHY and for low-power SC PHY.
3.2.2.1 SC PHY
This method is the simplest transmission option. A total of 12 MCS (1 to 12) are
defined, whereby support for MCS 1 to 4 is mandatory. The various MCS have differ-
ent modulations and code rates, and therefore also different throughputs. MCS1
(BPSK and code rate 1/2) can achieve 385 Mbit/s, MCS4 (BPSK and code rate 3/4) up
to 1.115 Gbit/s and MCS12 (16QAM and code rate 3/4) up to 4.620 Gbit/s. A complete
table of MCS1 to 12 for SC PHY is available at [1 - Table 21-18].
The data to be transmitted is scrambled, coded, modulated and blockwise transmitted.
Figure 3-8: SC PHY packet: Data processing.
● A low-density parity check (LDPC) coder is used for the encoding. It always uses a
codeword length of 672 bits, and the coding rate varies depending on the PHY. In
this case, code rates 1/2, 5/8, 3/4 and 13/16 are used.
● Depending on the data rate, various types of modulation are used (BPSK, QPSK or
16QAM). Each is shifted by π/2 to avoid zero crossings in the I/Q diagram. As a
result, the difference between the peak and average power remains low.
● The data are transmitted blockwise at 448 symbols per block. Another 64 symbols
are inserted between the individual blocks as guard intervals (GI) in order to pro-
vide a known reference signal to the receiver in the case of long data packets. The
complete block is therefore 512 (448 + 64) symbols in length. The GI consists of a
Ga64 Golay sequence and is always modulated with π/2-BPSK.

Figure 3-9: SC PHY data blocks: A data block is made up of 512 symbols (64 GI + 448 data).
3.2.2.2 Low power SC PHY
This method is set up similarly to the SC PHY, but it is optimized to save energy in
order to support small, battery-operated devices as well. In contrast to all other PHYs,
the LDPC is replaced by an energy-saving alternative, and unlike SC PHY, 16QAM
modulation is not used. A total of seven MCS (25 to 31) are defined, and all are
optional. The various MCS have different modulations and code rates, and therefore
also different throughputs. MCS25 (BPSK and code rate 13/28) permits rates of 626
Mbit/s to be achieved, and for MCS31 (QPSK and code rate 13/14) it is up to 2.503
Gbit/s. A complete table of MCS25 to 31 for low-power SC PHY is available at [1 -
Table 21-22].
The data to be transmitted is scrambled, coded, modulated and blockwise transmitted.
Figure 3-10: Low-power SC PHY packet: Data processing.

● A Reed-Solomon (RS 224,208) coder and a (Hamming) block code (N,8) are used
for the encoding. The data is also interleaved. The coding rate varies depending on
MCS.
● Depending on the data rate, various types of modulation are used (BPSK or
QPSK). Each is shifted by π/2 to avoid zero crossings in the I/Q diagram. As a
result, the difference between the peak and average power remains low.
● The data are transmitted blockwise at 512 symbols per block in this case as well.
Another 64 symbols are inserted between the individual blocks as guard intervals
(GI) in order to provide a known reference signal to the receiver in the case of long
data packets. The GI consists of a Ga64 Golay sequence and is always modulated
with π/2-BPSK. An additional eight symbols are inserted after every 56 symbols to
act as a guard block. The guard block is a copy of the final eight symbols from the
Ga64 sequence.A block of 512 symbols therefore includes 392 data symbols. A
final Ga64 is transmitted at the end of all blocks (i.e. at the end of the data range).
Figure 3-11: Low-power SC PHY data blocks.
3.2.3 OFDM PHY
To achieve the highest data rates, an OFDM mode was implemented. OFDM is also
used in 802.11n, LTE(A) or DVB-T.

A total of 12 MCS (13 to 24) are defined. The various MCS have different modulations
and code rates, and therefore also different throughputs. MCS13 (SQPSK and code
rate 1/2) permits rates of 693 Mbit/s to be achieved, and for MCS24 (64QAM and code
rate 13/16) it is up to the maximum possible rate of 6.757 Gbit/s. A complete table of
MCS13 to 24 for OFDM PHY is available at [1 - Table 21-14]. OFDM mode is optional,
but when it is implemented, MCS 13 to 17 must be supported.
Figure 3-12: OFDM packet preamble: STF consists of 17 Ga128 sequences and CE transmits Gv + Gu.
The basic packet structure is the same as the SC packet. However, to permit the
receiver to differentiate this packet from the SC packet, the sequence of Gu and Gv is
swapped in the CE field. The STF is made up of a total of 17 G128 sequences. Ga128
is first repeated 16 times, followed by one -Ga128. As a result, the STF is 17*128 =
2176 Tc in length. The CE field consists of one Gv512 and one Gu512, followed by a –
Gb128 sequence (the sequence of the SC-CE field is swapped). As a result, the CE
field is 9*128 = 1152 Tc in length.
Figure 3-13: OFDM header (64 bits).

The OFDM header is a total of 64 bits in length. The most important fields are
explained here: The basic structure is similar to the SC, except for two additional bits
specific to OFDM:
● MCS: Displays the modulation and coding scheme used in the data field
● Length (data): Specifies the length of the data field. For control, the range is 1 octet
to 262143 octets
how long it is
● Tone pairing type: Specifies the tone pairing used for MCS13 to 17 (see below)
● Last RSSI: Displays the power level of the last field received
The data to be transmitted is scrambled, coded, modulated and transmitted via OFDM.
Figure 3-14: OFDM: Data processing.
● A low-density parity check (LDPC) coder is used for the encoding. It always uses a
codeword length of 672 bits, and the coding rate varies depending on the PHY. In
this case, code rates 1/2, 5/8, 3/4 and 13/16 are used.
● Different modulations are used depending on the data rate (spread QPSK
(SQPSK), QPSK, 16QAM and 64QAM). The following special behaviors apply for
SQPSK and QPSK:
– Tone pairing is employed, where two subcarriers at a specified frequency offset
transmit the same data. This makes the transmission more robust to frequency-
selective interference. In static tone pairing (STP), which is mandatory for all
implementations, the frequency offset is always one half the subcarriers (336
subcarriers/2 = 118). There is also an optional dynamic tone pairing (DTP),
which is used to allow a response to varying channel conditions.
– In the case of SQPSK, only one half of the carriers are modulated with QPSK,
and the other half contain a (conjugated complex) copy of the data.
– In the case of QPSK, a matrix is additionally used for multiplexing at the I/Q
level. Bits 0 and 2 or bits 1 and 3 are combined into a four-way group via QPSK
modulation. Group 1 (bits 0 and 2) are transmitted in the first subcarrier and
group 2 (bits 1 and 3) on the associated tone pairing subcarrier, and so on.

Figure 3-15: Tone pairing with OFDM.
● A 512-point FFT is used for the allocation to the individual subcarriers. A total of
355 subcarriers at a distance of 5.15625 MHz are used, resulting in a total band-
width of 1830.47 MHz. The 355 subcarriers consist of 16 pilots, 3 DC and 336 data
carriers. The guard interval is 1/4 of a symbol. The pilots are located on carriers 10,
30, 50, 70, 90, 110, 130 and 150, each ±. The three DC carriers are located in the
middle (–1, 0 and +1) and are suppressed (nulled).
3.3 Beamforming
Transmission in the 60 GHz range is subject to greater free-space loss than in the 2.4
or 5 GHz range. The channel conditions can change dramatically during a connection
(for example, someone moves between a BluRay player and a projector during a 3D-
HD connection). Both can be managed in realtime by using beamforming. Because the
antenna size in the 60 GHz band is very compact, small and competitive antenna
arrays can be used. 802.11ad supports beamforming in realtime. During the beam
refinement process, training sequences for beamforming are sent between the trans-
mitter and receiver and evaluated. The best antenna weightings for each situation can
then be set.
Beamforming

Beamforming training sequences can be appended to all PHY packets (control, SC,
low-power SC and OFDM) for this purpose. The packet type and training length are set
accordingly in the respective header.
● Packet type:
– 0 Receiver training
– 1 Transmitter training
● Training length:
– Parameter n length -> AGC contains 4n fields
– TRN contains 5n fields
Figure 3-16: Beamforming TRN.
The antenna configuration cannot be changed during the "normal" packet ( STF, CE,
header, data).
The AGC field consists of 4n repetitions of five G64 sequences. Ga64 is used for SC
and OFDM packets, and Gb64 is used for control packets. In the case of a transmitter
packet, the antenna weighting can be changed for every individual AGC field; however,
it must be the same for the subfields. For a receiver field, the antenna weighting must
be the same as in the rest of the packet (preamble and data).
The training field consists of 5n repetitions of a block. This includes a copy of the CE
field from the preamble, followed by five G128 sequences. For the CE field, the same
antenna weighting must be used as in the packet (preamble and data).
All training fields must be transmitted with π/2-BPSK modulation.
3.4 Overview
This section provides a summary of the various PHYs.
Overview

Figure 3-17: Overview of different preambles: Top for control, middle for SC, and bottom for OFDM.
Overview

Figure 3-18: Overview of different headers: Top for control 40 bits, middle for OFDM 64 bits, and bot-
tom for SC 64 bits.
Overview

Figure 3-19: Overview of different PHYs.
Overview

Measurement requirements802.11ad - WLAN at 60 GHz
4 Measurement requirements
This section lists the T&M requirements for devices in accordance with 802.11ad. The
first section covers general requirements. Special requirements for the individual PHYs
are then explained in the second section.
4.1 General measurement requirements
The requirements in this section apply to all devices, regardless of which PHY is used.
4.1.1 Transmit mask
Even when the 802.11ad transmission takes place in the open ISM band, interference
of other applications must be minimized. This why a spectrum mask is applicable here,
as well.
Figure 4-1: Transmitter mask: The limits are relative to the power in the actual channel (±0.94 GHz).
At ±1.2 GHz it is -17 dB, at ±2.7 GHz it is -22 dB, and starting at ±3.06 GHz it is -30 dB
The limits apply relative to the nominal power (maximum spectral density). The mea-
surements are taken with a resolution bandwidth (RBW) of 1 MHz. The nominal band-
width is 1760 MHz for SC PHY and 1830.47 MHz for OFDM.
4.1.2 Center frequency tolerance (21.3.3.3)
A maximum deviation from center frequency of ± 20 ppm is permitted. For example,
this is ±1.2096 MHz for channel 2. In addition, the center frequency shall converge to 1
ppm of the nominal value within 0.9 μs after the start of the packet.
General measurement requirements

4.1.3 Symbol clock tolerance (21.3.3.4)
The maximum of ± 20 ppm also applies for the symbol clock. Both the symbol clock
and the center frequency shall be derived from the same reference.
4.1.4 Transmit Center frequency leakage (21.3.3.5)
The center frequency leakage shall be less than –23 dB relative to the total power for
SC PHYs, or +2.5 dB relative to the power of a subcarrier for OFDM.
4.2 Transmit rampup and rampdown (21.3.3.6)
Both the ramp-up and the ramp-down times (10 % to 90 %) should be less than 10 ns.
4.3 Requirements dependent on PHY or MCS
Both the requirements for the transmit EVM (see [1], chapter 21.4.4.1.2, 21.5.4.1.2 and
21.6.4.1.1) and the receiver sensitivity (see [1] chapter 21.3.3.9 Table 21-3) depend on
the PHY and/or MCS. In the case of the low-power SC PHY, no limits are specified for
Tx EVM.
Table 4-1: Summary of the limits for transmit EVM and eceiver sensitivity.
MCS Transmit EVM
(dB)
Receiver Sen-
sitivity
(dBm)
CPHY 0 DPSK - 6 - 78
SC PHY 1 π/2-PSK - 6 - 68
2 - 7 - 66
3 - 9 - 64
4 - 10 - 64
5 - 12 - 62
6 π/2-QPSK - 11 - 63
7 - 12 - 62
8 - 13 - 61
9 - 15 - 59
10 π/2-16QAM - 19 - 55
11 - 20 - 54
12 - 21 - 53
OFDM PHY 13 SQPSK - 7 - 66
Requirements dependent on PHY or MCS

MCS Transmit EVM
(dB)
Receiver Sen-
sitivity
(dBm)
14 - 9 - 64
15 QPSK - 10 - 63
16 - 11 - 62
17 - 13 - 60
18 16QAM - 15 - 58
19 - 17 - 56
20 - 19 - 54
21 - 20 - 53
22 64QAM - 22 - 51
23 - 24 - 49
24 - 26 - 47
LP SC PHY 25 π/2-BPSK n/a - 64
26 n/a - 60
27 n/a - 57
28 π/2-QPSK n/a - 57
29 n/a - 57
30 n/a - 57
31 n/a - 57
4.4 Transmit flatness for OFDM PHY (21.5.4.1.3)
For OFDM PHY a special spectrum flatness requirement applies, different for inner and
outer carriers:
● Subcarriers -146 to -2 and +2 to +146 -> +- 2 dB
● Subcarriers -177 to -147 and +147 to +177 -> +2/-4 dB
Transmit flatness for OFDM PHY (21.5.4.1.3)

Figure 4-2: Graphical summary of the requirements for TX flatness; the requirements are relaxed
starting with carrier 147.
4.5 Received channel power indicator (RCPI) measure-
ment (21.3.10)
The RCPI indicates the received RF power by a value in the range 0..255 in the power
range 0 dBm….-110 dBm in 0.5 dB steps. For more details see [1]. The RCPI differ-
ence to the actual power shall be at maximum ± 5 dB.
Received channel power indicator (RCPI) measurement (21.3.10)

Appendix802.11ad - WLAN at 60 GHz
5 Appendix
5.1 Golay sequences
In radiocommunications, training sequences are used for channel estimation. Prede-
fined sequences that are already known to the receiver are transmitted over the chan-
nel and evaluated by the receiver in order to estimate the channel. Complementary
Golay sequences are perfectly suited to this task because:
● the sum of the autocorrelation functions for two complementary Golay sequences
is ideal (lobes average out; see Figure 5-1)
● a Golay correlator is easy to implement
Figure 5-1: Examples for the ideal autocorrelation sum for a Golay sequence [2].
A Golay sequence is made up of bipolar (±1) symbols of the length n (Gn). A comple-
mentary sequence consisting of two sequences, each with a length of n, is identified as
Gan and Gbn, for example Ga128.
Figure 5-2: Example of a stage 3 Golay correlator; results in a length of n=8.
A fast correlator consists of the logarithm dualis of n blocks (i.e. seven blocks for
G128), that completes both correlations for a and b in parallel. For example, if the cor-
relator is fed with Gb sequences, peaks will appear at Output b.
In 11ad, sequences of varying lengths are used for different tasks (see [1] 21.11 for
sequences).
STF: G128. In this case the individual sequences are repeated, and a – sequence ter-
minates the STF.
● Control sends Gb128 first, followed by -Ga128
● All others send Ga128 first, followed by -Ga128
Golay sequences

● For STF, only the coding is used; the attributes of the complementarity remain
unused
CEF: G128. Four are combined into each G512
● Control and SC send Gu512 first, followed by Gv512
● OFDM sends Gv512 first, followed by Gu512
● The complementary attributes of the Gu and Gv Ssequences are used. The correla-
tion allows channel impulse response h to be determined, and from that channel
attribute H to be estimated. For example, sequence b is sent over the channel
(multiplication by h), resulting in h * b. In the correlator (multiplication by b), this
becomes b * b * h. For a, it is a * a * h. Adding up the two results leads to a * a * h
+ b * b * h, which can also be written as ( a * a + b * b ) * h. The sum of the auto-
correlation functions results in the impulse word, thus h remains.
Golay sequences are also used in the guard interval in SC PHY (G64) and in the
beamforming training sequences (G64 and G128).
5.2 Abbreviations
CE Channel Estimation (field)
CRC Cyclic Redundancy Check
dB Dezibel
dBm Dezibel Milliwatt
DMG Directional multi-gigabit
DTP Dynamic Tone Pairing
FFT Fast Fourier Transformation
GI Guard Interval
HCS Header Check Sequence
HD High Definition
HT High Troughput
LDPC Low Density Parity Check
MAC Medium Access Control layer
MCS Modulation and Coding Scheme
OFDM Orthogonal Frequency Division Modulation
PHY Physical Layer
PPM parts per million
RS Reed Solomon
RSSI Receive Signal Strength Indicator
Abbreviations

STF Short Training Field
STP Static Tone Pairing
TRN Training (field)
VHT Very High Troughput
WiGiG Wireless Gigabit Alliance
5.3 References
[1] IEEE: IEEE Std 802.11ad™-2012. Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications Amendment 3: Enhancements for
Very High Throughput in the 60 GHz Band
[2] Ming Lei and Ye Huang: CFR and SNR Estimation Based on Complementary Golay
Sequences for Single-Carrier Block Transmission in 60-GHz WPAN
References

Rohde & Schwarz802.11ad - WLAN at 60 GHz
6 Rohde & Schwarz
The Rohde & Schwarz electronics group offers innovative solutions in the following
business fields: test and measurement, broadcast and media, secure communications,
cybersecurity, radiomonitoring and radiolocation. Founded more than 80 years ago,
this independent company has an extensive sales and service network and is present
in more than 70 countries.
The electronics group is among the world market leaders in its established business
fields. The company is headquartered in Munich, Germany. It also has regional head-
quarters in Singapore and Columbia, Maryland, USA, to manage its operations in
these regions.
Sustainable product design
● Environmental compatibility and eco-footprint
● Energy efficiency and low emissions
● Longevity and optimized total cost of ownership
Certiﬁed Quality Management
ISO 9001
Certiﬁed Environmental Management
ISO 14001
Regional contact
● Europe, Africa, Middle East - customersupport@rohde-schwarz.com
Phone +49 89 4129 12345
● North America - customer.support@rsa.rohde-schwarz.com
Phone 1-888-TEST-RSA (1-888-837-8772)
● Latin America - customersupport.la@rohde-schwarz.com
Phone +1-410-910-7988
● Asia/Pacific - customersupport.asia@rohde-schwarz.com
Phone +65 65 13 04 88
● China - customersupport.china@rohde-schwarz.com
Phone +86-800-810-8228 / +86-400-650-5896
Headquarters
Rohde & Schwarz GmbH & Co. KG
Mühldorfstraße 15 | D - 81671 München
+ 49 89 4129 - 0 | Fax + 49 89 4129 – 13777
www.rohde-schwarz.com
This application note and the supplied programs may only be used subject to the conditions of use set forth
in the download area of the Rohde & Schwarz website.
R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG. Trade names are trademarks of the
owners.

802.11ad Guide - Wireless at 60GHz

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